The present invention relates to a steering stabilizer and quick coupling assembly for a multi-trailer combination or train comprising a self-propelled tractor constituting the No. 1 element of the so-called train; a towing, lead or first trailer constituting the No. 2 element of the train; a wheeled and steerable vehicle or dolly constituting the No. 3 element of the train; and a towed or second trailer constituting the No. 4 element of the train. One object of the invention is to minimize the oscillatory yaw behavior and rollover tendency between the second or last trailer or No. 4 element and its steerable dolly or No. 3 element. Another object of the invention is to provide quick coupling or uncoupling between the lead or first trailer and the towed or second trailer. A further object of the invention is to prevent off-tracking steering misalignment between the lead trailer or No. 2 element of the train and the steerable dolly or the No. 3 element of the train.
Numerous types of trailer dolly and hitch arrangements are known in the prior art as being adapted to allow one trailer to be hitched to and pulled behind another trailer, and these prior art dolly and hitch arrangements are mainly responsible for the problem of lack of stability experienced by the multitrailer combinations.
It is conventional, for example, to connect the lead or first trailer or No. 2 element to the steerable dolly or No. 3 element by means of a drawbar hitch arrangement. The drawbar hitch is pivotally connected at one of its ends to the rear frame portion of the lead trailer for both horizontal and vertical pivoting, whereas its other end is pivotally connected to the front end of the steerable dolly for pivoting only about a transverse horizontal axis. A problem with using a drawbar as the connection between the lead trailer and second trailer is that the second trailer receives no rollover support from the lead trailer.
Further, the majority of dollies or rotatable wheeled vehicles (No. 3 elements) used for coupling multi-trailer combinations, have no means to prevent or limit rotation of the No. 3 element in a horizontal plane about the hitch point on the rear of a pulling trailer. These conventional dollies are provided with a hitch on the forward end of the drawbar which allows the dolly or No. 3 element to freely pivot in such horizontal plane. Additionally, stability against rollover, i.e., pivoting about a longitudinal horizontal axis of the last trailer or No. 4 element with respect to the towing or first trailer or No. 2 element, is exceptionally low because the No. 3 element has a conventional trailer coupler, or fifth wheel, above the axle which is pivotally engaged with the towed or second trailer or No. 4 element in the same manner as the conventional fifth wheel on the tractor or No. 1 element is pivotally engaged with the first trailer or No. 2 element. Thus, the last trailer receives no roll support from the lead or towing semi-trailer, particularly in evasion type maneuvers.
The steering stabilizer and quick coupling assembly of the present invention is applicable to all multi-trailer trailer tractor combinations, but it finds special application for tandem or double-bottom tankers because of their unique stability problems. Double tankers typically carry approximately 9,000 gallons of fuel in the lead or towing tanker and approximately 7,000 gallons of fuel in the trailing or second tanker. The lead trailer or No. 2 element by law is the heaviest vehicle of the so-called train. The obvious reason for using tandem tankers is to reduce the number of tractors and operators required, theoretically reducing the likelihood of accidents and decreasing costs including costs of operation.
Unfortunately, the rollover stability and sway stability of known double bottom tanker combinations is exceptionally low, particularly in accident-evasion type maneuvers. This problem is accentuated because, unlike other multi-trailer combinations, the tandem tankers are frequently towed when they are only partially loaded with fuel. The sudden movement or sloshing of the fuel within the tankers during high speed or emergency maneuvers drastically decreases the roll and sway stability of the last trailer or No. 4 element.
The double tanker combination has definite stability problems, with the primary problem residing in the behavior of the second trailer or No. 4 element of the train. In emergency lane change maneuvers, the second trailer amplifies the yaw motions of the tractor and towing trailer. At a high frequency range of steering inputs, the second trailer or No. 4 element experiences roll or overturning accelerations which are more than twice as large as that experienced at the tractor or No. 1 element. In addition to oscillatory yaw behavior, the second trailer has a low level of basic rollover immunity. In a steady turn situation, the rollover limit of the loaded second trailer is approximately 20% lower than that exhibited by most heavy commercial vehicles. For emergency lane changes, the double tanker will experience rollover at a maneuvering level which is less than half of the maneuvering level that is needed to roll over conventional tractor, semi-trailer combinations. Thus, the known double tanker combination exhibits an exceptionally low degree of yaw and roll stability with the second trailer or No. 4 element contributing most significantly to the problem.
Another problem associated with conventional trailer dolly and drawbar hitch arrangements is that during sharp turning maneuvers, an off-tracking steering misalignment occurs between the lead trailer or No. 2 element of the train and the steerable dolly or No. 3 element of the train. During normal steering maneuvers by the tractor and good road conditions, a conventional A-frame drawbar provides adequate trailer connection between the lead trailer and the second trailer such that the second trailer generally follows the path of the towing or lead trailer. However, during sharp turning maneuvers and off-road conditions, a conventional drawbar connection causes steering misalignment between the rear wheels on the lead trailer and the wheels supporting the steerable dolly which results in additional wear on the steerable dolly wheels and generally poor steerability. Thus, there has been a need for a connection between the lead trailer and steerable dolly which prevents off-tracking steering misalignment between the lead trailer and steerable dolly thereby improving steering and maneuverability.
A further problem with conventional drawbar connections between the lead trailer and steerable dolly is that it is difficult and inconvenient to connect or disconnect the forward end of the drawbar and the lead trailer. Maneuvering the lead trailer into a position where it is aligned with the forward end of the drawbar is a time-consuming process. After the rear end of the lead trailer and drawbar are aligned for attachment, the actual hook-up using conventional fasteners, involves a considerable amount of additional time and labor. Thus, there has been a need for a quick coupling and uncoupling mechanism between the lead trailer and towed or second trailer to replace the conventional A-frame drawbar thereby reducing the labor and time involved in making the necessary connection.
It is accordingly the general objective of the present invention to provide a rollover and steering stabilizer apparatus between a lead or towing trailer (No. 2 element) and a towed or second trailer (No. 4 element) which minimizes oscillating yaw behavior of the second trailer, provides roll support from the lead trailer to the second trailer, and increases the basic rollover immunity of the second trailer. Another objective of the present invention is to provide a mechanism for quick coupling or uncoupling between the lead or first trailer and the towed or second trailer. A further objective of the invention is to prevent off-tracking steering misalignment between the lead trailer and the steerable dolly during sharp turning maneuvers.